Dyed surgical gut and process



July 31, 1962 A. F. SANTORO ET AL 3,047,352

DYED SURGICAL GUT AND PROCESS 2 Sheets-Sheet l Filed Jan. ll, 1960 DEIA! `July 31, 1962 A. F. SANTORO ET AL 3,047,352

DYED SURGICAL GUT AND PROCESS Filed Jan. l1, 1960 2 Sheets-Sheet 2 @www 3,@4752 DYED SURGECAL GUT AND PROCESS Anthony F. Santoro, Bound Brook, NJ., and Walter P. Hivos-dek, Fairfield, Conn., assignors to ltiicon, lne., a corporation of New .lersey Filed Jan. l1, i960, Ser. No. 1,470 8 Claims. (Cl. 8 3) The present invention relates to surgical gut dyed with indigo and the process by which this product is produced; more particularly the invention relates to such dyed gut and the process for producing it wherein the desirable characteristics of the gut such as strength and dimension are preserved and wherein the dye is combined with the gut in such a way that it will not disassociate when exposed to alcohol packing iluid or when exposed to materials present in the human body such as blood serum.

Animal gut is commonly used as a material from which surgical sutures are made. Although commonly referred to as catgut, sutures are more frequently made from the intestines of sheep. Animal intestines are constituted of protein collagen and in some instances surgical sutures may be made from regenerated collagen rather than being cut directly from the animal intestines. The invention is equally applicable to dyed sutures formed of regenerated collagen as well as those formed directly from animal intestines.

though surgical gut has many advantages as a material for surgical sutures, it is light in color and often.

does not provide much visual contrast with the tissue in which it is used. This situation adds to the difficulty of delicate surgery. A particular example of surgical operations in which this problem is acute is Ophthalmological surgery, that is, eye surgery. It can readily be appreciated that the surgeons job would be greatly facilitated by the use of a suture of dark color presenting a good contrast against a tissue background such as the cornea of the eye.

The many customary dyeing processes for other materials are not readily adaptable to dyeing surgical gut due to the special requirements that exist. One of the requirements is that the desirable characteristics such as strength and uniform dimension of the surgical suture not be lost in the dyeing process. Another important requirement is that the dyeing material not bleed out when exposed to alcohol packing iluid or to blood serum and the like in the human body. The bleeding of dye into surrounding tissue would create a permanent marl so that, in the case of eye surgery for example, the cornea of the eye could in eiect be tattooed with a stitch pattern in the event of bleeding of the suture dye. This is obviously a highly undesirable effect which must be avoided.

The nature of the invention will be understood from the following description and from the drawings in which:

FIGURE l is a flow diagram of a preferred process for producing the dyed surgical gut;

FIGURE 2 is a schematic diagram of a forni of apparatus usable in preparing dyed surgical gut according to the invention; and

FlGURE 3 is a horizontal sectional view of the suture support rod of FlGURE 2 taken along the line 3-3 in FIGURE 2.

A preferred process and apparatus for producing dyed surgical gut according to the present invention is shown in FIGURES l, 2 and 3. Preparation of the dye Solution is initiated by adding several drops of 1% Aerosol OT solution to 2 grams of drug and cosmetic dye, Blue No. 6, to form a paste. Aerosol OT is an ester of sulfonated'dicarboxylic acid; all solutions are in water unates Fatent @t hdd-7,352

less otherwise stated. Drug and cosmetic dye, Blue No. 6, is available from H. Kohnstamm & Company, Inc. under the name of Atlas Colors. Drug and cosmetic dye, Blue No. 6, is formed of at least pure indigo (Indigotin, ClHlONgOZ). Although other dyes of nontoxic non-bleeding characteristics could be utilized, the above-described drug and cosmetic dye, Blue No. 6, is preferred for the dyeing of surgical gut to achieve particular advantages according to the present invention. Any suitable anionic wetting agent may be substituted -for the Aerosol OT solution.

Preparation of the dye paste may be accomplished in a 10 milliliter container as indicated at ll in FiG- URE l and may be completed by stirring the paste for one minute.

As indicated at l2 in FIGURE l, six drops of 25% sodium hydroxide solution are next added to the paste and stirred. Although it will be observed that, in the particular process disclosed in FIGURE l, the sodium hydroxide is added in two steps, it may in some cases be preferred to add all of the sodium hydroxide in a single step. The total amount of sodium hydroxide required is that suthcient to permit the hydrosultite powder to change the dye to leuco form.

Following the addition of sodium hydroxide and the stirring of the mixture as indicated a fr in FEGURE l, four grams of sodium hydrosuhite powder are added to the mixture as indicated at 13. The sodium hydrosulte is a reducing agent which is utilized for transforming the indigo dyeing solution to leuco form, As in the case of the sodium hydroxide, this material can be added in a single step rather than in two steps as indicated in FIGURE l. The total amount of sodium hydrosuliite should be at least approximately one and a half times the amount of indigo dye material by weight.

After the sodium hydrosuliite is added and mixed with the previously added materials, 30 milliliters of distilled water is added as indicated at 14 in FIGURE l and the mixture is allowed to stand for twenty minutes; thereafter the dye solution may be diluted with distilled water to a suitable volume to provide a bath for the dyeing of the surgical gut. In FIGURE l at l5 this volume is indicated to be two liters by way of example. It will be understood that particular volumes have been given by way of example in FIGURE l but that the size of the batches can be increased or diminished by increasing the amount of the constitutents or decreasing the amount of the constituents proportionately.

Following the dilution of the dye mixture as indicated at 15, two grams of sodium hydroxide pellets and three grams of sodium hydrosultite powder may be added to complete the mixture as indicated at i6. A further check on the proper amount of sodium hydrosultite may be made by checking the pH, which should be about pI-I 11-12 at this stage of the process.

Some time is required for the reaction between the sodium hydrosultite, the indigo dye and the other materials of the mixture. This time may be provided by allowing the mixture to stand for approximately 16 hours. The reaction may be expedited if desired, for example, by blanketing with nitrogen or another inert gas, a stirring mixture, to exclude oxygen, in which case the reaction time may be reduced to two hours or less. The completion of the reaction will readily be visible by observing the color of the dye solution, which should be clear and straw yellow in color. Before using the dye solution the pH should be brought to approximately pH l() by the addition of dilute hydrochloric acid as indicated at 17 in FIGURE 1.

The exposure of the surgical gut to the dye solution may readily be accomplished in an elongated vertical container as indicated at 1S in FIGURE 1. A more detailed showing of the bath and the manner of suspension of surgical sutures therein is shown in FIGURES 2 and 3. A tubular dyeing cylinder of elongated form is provided as shown at 51 having an open mouth 52 at the top thereof and an orifice 53 at the bottom for draining the solution from the cylinder. A clamp 54 or a valve is provided for controlling the ilow of liquids out of the cylinder 5I. The cylinder may be supported by any suitable means such as a clamp 55 and a conduit S6 is provided at the upper end of the dyeing cylinder connected to a water supply so that the contents of the cylinder may be washed by a flow of running tap water.

A support for the surgical gut to be bathed in the dyeing cylinder is provided comprising a rigid rod 57 having aiixed near the ends thereof separators 58 for facilitating the attachment of surgical sutures to the rod 57. The separators may take the form of gear shaped members as indicated in FIG. 3.

Sutures 59 may be secured to the supporting rod 57 by placing them between the teeth of the gear shaped members E@ at each end of the rod 57 and securing them at each end to the rod just beyond the gear shaped members 58 by means of clamps 59 or by tape or by other suitable means. The sutures 61 are secured to the rod S7 under slight tension which Serves to maintain their strength and dimension.A Otherwise, the surgical gut will shrink, its cross-sectional dimensions will be increased and its strength will be reduced when exposed to the dye bath due to hydration of the protein collagen.

After mounting the sutures 6l on the rod 57, rod and sutures together may be placed in the dyeing cylinder 5I. As an alternative to the arrangement shown in FIG. 2 the sutures may be Weighted at one end and hung in the dye solution in such a way that the Weight provides the desirable tension provided by the rod 57 in FIGS. 2 and 3.

Obviously, still other apparatus may be provided for suspending the sutures in a dyeing solution which will provide thetension on the sutures to produce the desirable end product according to the present invention. For example, a larger container could be provided with more elaborate supporting structure to support a larger number of sutures. In some instances it may be desired to secure the surgical gut in a long strand which may be moved over pulleys and the like through various solutions in a continuous process.

In the specic process shown in FIGURE 1 10() strands of surgical gut each of 60 inches length are suspended in the apparatus of FIGURE 2 which contains 1500 milliliters of dyeing solution as indicated at I8 in FIGURE 2. The strands of gut are agitated at room temperature for ve minutes. This may be accomplished by gently moving the rod S7 up and down in the dyeing cylinder 51. Following the exposure of the surgical gut to the dyeing solution, the dye solution is drained as indicated at I9 in FIGURE l and a 6% hydrogen peroxide solution is placed in the dyeing cylinder to oxidize the dye, at which time it will assume its permanent dark blue color. Any other suitable oxidizing process might be utilized to accomplish the same result but the hydrogen peroxide bath is a quick and eicient method of electing this result.

The dye solution drained from the dyeing cylinder may be returned and mixed with any unused solution as shown at 17 in FIGURE l and this solution may be utilized for dyeing subsequent batches of surgical gut. The specitic amount of dye shown in the specic process of FIGURE l will be suflicient to dye at least 200 sixty inch strands of surgical suture containing a total of about l0 grams of material (protein collagen).

The oxidation of the dye by hydrogen peroxide will take approximately 30 seconds after which the hydrogen peroxide may be removed from the dyeing cylinder as indicated at 21 in FIGURE l, and a .2 M buffer solution of approximately pH 3.6 may be placed in the dyeing d. cylinder. A suitable butter solution is .2 M acetate butter consisting of .2 M sodium acetate and .2 M acetic acid.

After Washing lin the buffer solution for 45 seconds the surgical gut may be rinsed with owing water for three minutes as indicated at 22 in FIGURE 1.

Following the tap water rinse the surgical gut is air dried under slight tension as indicated at 83 in l. The gut may be dried on the same rack or support used for supporting it in the drying and rinsing solutions or may alternatively be transferred to a different drying rack of any suitable type. Following the air drying, the gut is dehydrated in air for eight hours at temperatures increasing gradually from room temperature to 119 C. as indicated at 24 in FIGURE l. The particular type of apparatus utilized for this step of the process is not especially critical and any controlled heat drying apparatus may be utilized.

Following dehydration the dye is set by exposure to a high temperature in an anhydrous atmosphere. In the process set forth in FIGURE l, this step is provided by a bath in high -liash naphtha at 310 F. -for a period of one hour.

Following the high temperature bath, the surgical gut is substantially completely processed; however, to entirely eliminate the possibility of slight coloration of the alcohol packing tluid in which the suture is packed, the surgical gut may be rinsed in 99% isopropyl alcohol. This will remove any slight amount of unset dye material and wiil prevent noticeable coloration of the alcohol packing tiuid in which the surgical sutures may be packed. It will be understood that the alcohol rinse will not always be necessary and represents merely an extra precaution to prevent bleeding of the dye surgical gut in packing solution.

In addition to the variations in materials and steps of the process shown and suggested, other variations will be obvious to those of ordinary skill in the art and accordingly it is desired that the scope of the invention not oe limited to the particular article and process disclosed but that it should be limited solely by the appended claims.

What is claimed is:

1. Dyed surgical gut comprising unhydrated protein collagen impregnated with indigotin in a proportion of approximately one part indigotin to from tive to one hundred parts protein collagen by Weight.

2. A dyed surgical gut suture comprising a strand of unhydrated protein collagen impregnated with indigotin in a proportion of approximately one part indigotin to from tive to one hundred parts protein collagen by weight.

3. The process of dyeing surgical gut comprising the steps of impregnating surgical gut formed of protein collagen with indigotin solution in leuco form, said gut being secured under slight tension to retard deformation and hydration, and exposing said gut to an oxidizing agent to change the color of said indigotin.

4. The process of dyeing Surgical gut comprising the steps of impregnating surgical gut formed of protein collagen with indigotin solution in leuco form, said gut being secured under slight tension to retard deformation and hydration,l exposing said gut to an oxidizing agent to change the color of said indigotin, and setting said dye by exposing said gut to a temperature of approximately 309 F. in an anhydrous environment.

5. The process of dyeing surgical gut formed of proteiun collagen comprising the steps of preparing a dyeing solution comprising one part indigotin and `at least one and one-half parts sodium hydrosultite in a relatively large volume of water and reduced to leuco form, adjusting the pH of the mixture to approximately pI-I l0, impregnating surgical gut with said mixture, oxidizing said surgical gut by exposure to an oxidizing agent, dehydrating said surgical gut, and setting said dyed surgical gut by exposure to a temperature of approximately C. in an anhydrous environment.

6. The process of dyeing surgical gut formed of protein collagen comprising the steps of preparing a dyeing solution comprising one part indigotin and at least one and one-half parts sodium hydrosulte in a relatively large volume of water and reduced .to leuco form, adjusting the pH of the mixture to approximately pH 10, impregnating surgical gut While under tension `with said mixture, oxidizing said :surgical gut by exposure to an oxidizing agent, dehydrating said surgical gut and setting said dyed surgical gut by exposure to a temperature of approximately 155 C. in an anhydrous environment.

7. The process of dyeing surgical gut formed of protein collagen comprising the steps of preparing a dyeing solution comprising one part indigotin and at least one and one-half parts sodium hydrosuliite in a relatively large volume of Water and reduced to leuco form, adjusting the pH of the mixture to approximately pH 10, impregnating surgical gut While under tension with said mixture, the ratio by Weight of said surgical gut with respect to said indigotin in said mixture being no more than 100, oxidizing said surgical gut by exposure to an oxidizing agent, dehydrating said surgical gut and setting said dyed surgical gut by exposure to a temperature of approximately 155 C. in an anhydrous environment.

8. The process of dyeing surgical gut formed of protein collagen comprising the steps of preparing a dyeing solution comprising one part indigotin and at least one and one-half parts sodium hydrosulte in a relatively large volume of Water and suiicient sodium hydroxide to permit the indigotin to be changed to leuco form, adjusting the pH of the mixture to approximately pH l0, impregnating surgical gut with said mixture while under tension for at least approximately ive minutes, the ratio by weight of said surgical gut With respect to said indigotin in said mixture being no more than one hundred to one, oxidizing said surgical gut by exposure to hydrogen peroxide, Washingr said surgical gut with a buier solution, rinsing said surgical gut with flowing water, air drying said gut under slight tension, dehydrating said surgical gut over a period of approximately 8 hours at a temperature gradually increasing from room temperature to C. approximately, and setting said dyed surgical gut by exposure to a temperature of approximately C. in an anhydrous environment.

References Cited in the file of this patent UNITED STATES PATENTS 1,382,715 Davis June 28, 1921 2,297,701 Hug Oct. 6, 1942 2,524,073 Olpin et al. Oct. 3, 1950 2,748,774 Novak June 5, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,047,352 July 31 1962 Anthony F. Santoro et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 13, for "10" read IOO Signed and sealed this lst day of January 1963.,

(SEAL) Attest:

ERNEST w. swIDER DAVID L- LADD Attesting Officer Commissioner of Patents 

3. THE PROCESS OF DYEING SURGICAL GUT COMPRISING THE STEPS OF IMPREGNATING SURGICAL GUT FORMED OF PROTEIN COL- 